In recent years, it has been sincerely desired that the emission amount of carbon dioxide be reduced in order to cope with the air pollution and the global warming. In the automobile industry, expectations have been centered on such reduction of the emission amount of carbon dioxide by introduction of the electric vehicle (EV) and the hybrid electric vehicle (HEV). Therefore, development of an electric device such as a secondary battery for driving a motor, the electric device serving as a key for practical use of these vehicles, has been assiduously pursued.
As the secondary battery for driving a motor, a lithium ion secondary battery having high theoretical energy attracts attention, and at present, development thereof progresses rapidly. In general, the lithium ion secondary battery has a configuration in which a positive electrode, a negative electrode and an electrolyte located there between are housed in a battery case. Note that the positive electrode is formed by coating a surface of a current collector with positive electrode slurry containing a positive electrode active material, and the negative electrode is formed by coating a surface of a negative electrode current collector with negative electrode slurry containing a negative electrode active material.
Then, in order to enhance capacity characteristics, output characteristics and the like of the lithium ion secondary battery, selection of the respective active materials is extremely important.
Heretofore, a lithium ion battery cathode composition, which has Formula (a) Liy[M1(1-b)Mnb]O2 or Formula (b) Lix[M1(1-b)Mnb]O1.5+c, has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2004-538610). Note that, in the formulae, y ranges like: 0≦y<1; b ranges like 0<b<1; and c ranges like: 0<c<0.5. M1 represents one or more of metallic elements. However, in a case of Formula (a), M1 is a metallic element other than chromium. Then, this composition has a single-phase form having an O3 crystal structure that does not cause phase transition to a spinel crystal structure when a cycle operation of a predetermined complete charge/discharge cycle is performed.